Radio Receiver R-390/ URR
Providing for the reception of voice, continuous wave (cw), single-sideband (ssb) and frequency-shift signals, over a frequency range of 0.5 to 32 megacycles.

The receiver is a superheterodyne of the multiple-conversion type, triple conversion is used for the lower frequencies (0.5 to 8 mc) and double conversion is used for the higher frequencies (8 to 32 mc).

The manual covers field and depot maintenance for Radio Receiver R-390/ URR.

It includes instructions appropriate to third, fourth and fifth echelons, for troubleshooting, testing, aligning and repairing the equipment and replacing maintenance parts.

It also lists tools, materials and test equipment, for third, fourth and fifth echelon maintenance.

Detailed functions of the equipment are covered in the theory sections.